High-frequency amplifier



Patented Oct. 28, .1947

PATENT "OF Fl-CE' men-FREQUENCY AMPLIFIER William Hotine, Water-town, Mass.y asstg nor to Federal Telephone and Radio Corporation, Newark N. J-., a 'corporation of Delaware Application January '30, 1943, Serial No. 474,173

7 Claii'ins. 1

This invention relates to mprovements in high freq ency amplifiers, and more particularly to amplifiers of the type in which hollow metal cyl- "inders forming part or a "concentric line'surfolm'd and enclose a vacuum tube to form a unitary amplifier structure and circuit.

An object of this invention is to provide an estremdy stab1e amplifier 'o'rxthe type adapted "to be used atultra-hrghrrequencies.

Another obfie'c't or this invention is to provide a novel tuning "arrangement for high frequency amplifiers. 7

Generally speaking, the invention is directed to the novel construction of a high frequency amplifier "in which "two "concentric lines, one con rented toth'e anode 'and'tlre'otrrer to the cathode of an enclosed Vacuum tube, are isolated from one another except through e. common ground, and are both-isolated "from each other "by the grid by a "construction which separatesthe two lines; a subsidiary feature of this invention is directed to a novel ariengement for accurately tuning such "an amplifier. These and other features of the invention will become apparent from the following description 'o'f a preferred embodiment thereof, illustrated in the a'cc'ompanying drawings in-which:

Fig. *1 is a front elevation partly in section of the Structure formed in accordance with the'presei'i't invention; and r Fig. 2 is a simplified circuit diagram of the amplifier illustrated in "Fig. 1.

'As shown in the drawings, the amplifier consists primarily of 'a pair "of hollow meta-l cylinde'rs E and -12, which are positioned coaxially wi th thelrepposed-ends s aced'rrom one another. vacuum tube P3, such as a triode is mounted in some suitable mairmerwltllin the opposed ends the cylinders. The vacuum tube fl is prefe ra bly of the type :having oppositely positioned anode and cathode elements 1 6 and It res ecti vly, and a centrally "positioned grid having "a -e enerefilly radially extending tern'linal 24 passing through the -surrounding glass envelo e In aceorda-nce the present invention, the m'tal "cylinders 1'0 an'l F2 the outer :eondoctors or *eeaxial lin'es coupled in an suitable manner to the anode and c'ath'ode of the tube 14. variousiceuplingarrangementsknown'to tlre *art and which rerm noipart of th-i's invention per :se Fma he used. In Fig. 1, .I have indicated an inner rnetezl conductor 26 which, with the outer zmetal icylinkier t! :rer m's one coezxiel cine will be coupled to the cathode L8. nsfimi-larzmn'er -conductor (not show-n) will be used in connectl'on with the outer cylinder H] and coupled to the anode 1 6, v The opposedends 0f the outer cylinders Wand 12 are respectively formed with outwardl .extendin radial'fia'nges 2B and 3 0. About the end faces off these flanges are respectively positioned rings "32 and 34 of suitable insulating material such 'as polystyrene. Between the insulating 'r-irigsextends the radial grid terminal 2 4 and an outwardly extending gr-itl lead 35. The two icy-1- inders together with their flanged ends and the intermediate insulating rings, the grid terminal and the grid lead are drawn together by means or split insulating :blocks 36 and 38 which surround the rear faces of the end flanges '28 and and also the periphery of these flanges as well as the periphery of the insulating rings 32 and '34, .and are drawn together by suitable means such as screws "40. "The fgrid terminal 315 of which there be one or more, extend radially "outwardly from lma'tween ith'ese split blocks. The whole mplifierunitiis preterabl-y mounted upon a. grounded metal plate 42, the split insulating blocks :36 and 38, which may have :a

rectangular shape resting on the metal plate and supporting the center of *the amplifierun'it, the individual outer cylinders [0 and 152 "being .sup- :ported by means such as surrounding metail straps 44 which at the same time serve to electrica'lly connect the surface of the cylinders with the ground :plate 42.

Coupling may 'be made to the plate :and cathode lines by the means illustrated at 46, 48 and 4B, 48, As shown in the :right hand side -of Fig. 1, the outercylinder [-2 may be formed with an opening surrounded by a projecting ring '46. Coneentrically through the opening is positioned a. rod 48, connected to theinner cylinder 26. The rod 43 and the ring '48 may, together, form a coaxial cable connector.

The structure so far described provides an amplifier circuit "of the type indicated in Fig. 2. The cathode line "is represented in Fig. 2 by the inductance's l 2 and 26 corresponding to the outer and inner cylinders 'ofFig. 1 while the plate line rs' indicated by the induct'ances I0 and I0, corresponding 'to t'h'e outer and inner cylinders on the other side. The grid will be further coupled to the outer cylinders 10 and l? by capacitors C1, C2 which are formed-by the grid terminal -24 as'on'ec'ommon plate and the flanges Hand 30, separated therefrom by the insulating rings 32 and M, "the "two outer plates. Since :such capacitors will have a relatively poor dielectrimcon- 3 stant by reason of the thick rings 32 and 34, they will at high frequencies have some resistance as represented by R1 and R2. By reason of the construction illustrated in Fig. 1 and the resulting circuit as shown in Fig. 2 it will be seen that the plate line is isolated from the cathode line by the grid, while the outer conductors l and I2 of the plate and cathode lines respectively are also isolated from one another by the grid flange, the only connection at high frequencies between them being through the relatively long inductive electrical path offered by straps 44 and the metal base 52. It has been found by test and experimentation that such an arrangement provides an amplifier which is externally stable at Very high frequencies, for example, in the neighborhood of 600 megacycles.

I claim:

1. A high frequency amplifier comprising a pair of hollow metal cylinders each having a radially flanged end, a base, means coaxially mounting said cylinders on said base with their flanged ends opposed to one another, a vacuum tube mounted within the opposed ends of said cylinders, said tube having a terminal extending radially outwardly between the opposed cylinder flanges, a pair of insulating rings mounted on opposite sides of said terminal and against the respective end faces of the opposed cylinder flanges, a split insulating block surrounding the periphery and the rear faces of the flanges, clamping means drawrings and tube terminals between, whereby said Tuning of the aforedescribed amplifier at ultrahigh frequencies must of necessity be very accurate. In accordance with the present invention such accurate tuning is provided by means of a short circuiting ring 56 slidably mounted between the inner and outer conductors of the coaxial lines. Movement of the short circuiting ring 56 is effected through a pair of externally threaded arcuate segments 52 and 54, oppositely slidably mounted on the surface of the inner conductor 26. The arcuate segments 52 and 54 are attached in any suitable manner at one end to the short circuiting ring Ell while their other ends extend outwardly beyond the outer cylinder l2 and have threaded thereover a ring 56 provided with an outwardly extending radial flange 51. The flange 51 of the ring 56 is adapted to be positioned for rotation but against longitudinal movement in an internal annular groove 58 which may be builtup on the end of the outer cylinder it through a surrounding ring 59 having an inwardly extending flange for limiting the outward longitudinal movement of the flange 5'! and defining one side of the annular groove 58. The ring 59 is mounted on the cylinder l2 through a spacing ring 60, the end of which-may serve to form part of the boundary of the groove 58. A disc 62 positioned within the end of the cylinder I2 and having an end flange flush with the end of the spacing ring 6! forms the rest of the inner boundary of the annular groove 53. Means such as screws (is will hold the rings 59 and 60, and disc 62 together and to the end of the cylinder 12. Threaded on the outer surface of the ring 56 are a pair of thin knurled discs (55 and 68. When these are locked together they will rotate the ring 56 which, because of its restraint in the lateral direction by the groove 55 will, through its threaded engagement cause longitudinal movement of the segments 52 and 54 through radial slots in disc 62, and thus a sliding adjustment of the shortcircuiting ring 58. This arrangement permits a very fine control of the movement of the shortcircuiting ring.

While the novel tuning arrangement illustrated has been described, particularly in connection with the cathode line I2, 26, a similar arrangement may be utilized for tuning'the plate line, and similar parts have been indicated at 52, 54', 59', 66', and 68' at the left hand side of Fig. 1.

while I have described above the principles of my invention in connection with specific applications, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and the accompanying claims.

cylinders are held against longitudinal movement relatively to one another, a second cylinder mounted concentrically within one of said pair of hollow cylinders and forming a concentric line therewith, a, slidable short-circuiting ring frictionally mounted between the two concentric cylinders, and adjusting means positioned on the end opposite the flanged end of the one cylinder for moving said short-circuiting ring.

2. An amplifier according to claim 1, in which said last means includes a pair of externally threaded arcuate slides positioned diametrically opposite on the inner cylinder and connected at one end to said short-circuiting ring, an internally threaded ring threadably engaging said slides at their other ends, said threaded ring having an outwardly extending radial flange on its inner end,

' means connected to the opposite end of the one outer cylinder forming an internal annular groove receiving said radial flange, whereby said threaded ring may be rotated but is restrained in longitudinal movement by said groove, and means for rotating said threaded ring for causing longitudinal sliding movement of said slides and shortcircuiting ring through the engagement between said internally threaded ring and the externally threaded slides.

3. An amplifier according to claim 1, in which said base is a metal plate, and said cylinder mounting means comprises metal straps electrically connecting the outer surfaces of each cylinder to said plate and said surfaces to one another through said plate, in combination with an electrical ground connected to said plate.

4. A high frequency amplifier comprising a pair of hollow metal cylinders, each having a radially flanged end, a metal base, means coaxially mounting said cylinders on said base with their flanged ends opposed to one another and simultaneously electrically connecting the outer surfaces of said cylinders to said base, an electricalground connected to said base, a vacuum tube mounted within the opposed ends of said cylinders, said tube having a terminal extending radially outwardly between the opposed cylinder flanges, a pair of insulating rings mounted on opposite sides of said terminal and against the respective end faces of the opposed cylinder flanges, a split insulating block surrounding the periphery and the rear faces of the flanges, and clamping means drawing said split blocks together, and pulling said flanges toward one another with the insulating -rings and tube terminal between them, whereby said cylinders are held against longitudinal movement relatively to one another, and said terminal is capacitatively coupled to said cylinders through said insulating rings and flanges.

5. An amplifier according to claim 4, in combination with a second pair of cylinders, one positioned concentrically within each hollow cylinder and forming a concentric line therewith, and in which said vacuum tube includes a cathode connected to one inner cylinder, an anode connected to the other inner cylinder and a grid connected to said terminal.

6. A concentric line having an outer hollow metal cylinder surrounding a concentric metal cylinder, and a slidable short-circuiting ring intermediate the two cylinders, and means for adjusting the position of said ring, comprising a pair of externally threaded arcuate slides positioned diametrically opposite on the inner cylinder and connected at one end to said shortcircuiting ring, an internally threaded ring threadably engaging said slides at their other end, said threaded ring having an outwardly extending threaded flange on its inner end, means connected to the adjacent end of the outer cylinder, forming an internal annular groove receiving said radial flange, whereby said threaded ring may be rotated but is restricted in longitudinal movement by said groove, and means for rotating said threaded ring for causing longitudinal REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,402,612 Dodington June 25, 1946 2,284,405 McArthur May 26, 1942 2,190,668 Llewellyn Feb. 20, 1940 1,930,505 Brown Oct. 17, 1933 2,216,169 George et al Oct. 1, 1940 

